Mattress spring core construction over the years has been a continuously improving art with advancements in materials and machine technology. A well-known form of spring core construction is known as a Marshall spring construction wherein metal coil springs are encapsulated in individual pockets of fabric and formed as elongate or continuous strings of pocketed coil springs. In an earlier form, these strings of coil springs were manufactured by folding an elongated piece of fabric in half lengthwise to form two plies of fabric and stitching transverse and longitudinal seams to join the plies of fabric to define pockets within which the springs were enveloped.
More recently, improvements in spring core constructions have involved the use of fabrics which are thermally or ultrasonically weldable to themselves. By using such welding techniques, these fabrics have been advantageously used to create strings of individually pocketed coil springs wherein transverse and longitudinal welds, instead of stitching, are used to form the pockets encapsulating the springs. One such fabric is a non-woven polypropylene fabric.
One of the long recognized advantages of bedding or seating products incorporating springs when compared to bedding or seating products made of foam is the coolness or lower temperature of the product. In other words, when a user sleeps on a mattress made with coil springs, the sleep surface is cooler than the sleep surface of a mattress made with foam. However, a mattress made with pocketed coil springs may be warmer than a mattress made with conventional springs.
Once strings of pocketed springs are constructed, adjacent strings are typically glued together to form a pocketed spring assembly of the desired size for a mattress, cushion or the like. For example, multiple strings may be arranged in a row pattern corresponding to the desired size and shape of a mattress or the like, and adjacent strings of strings glued together. The result is a unitary assembly of pocketed coil springs serving as a complete spring core assembly. However, the weak point in the pocketed spring assembly is along the glue lines.
Therefore, there remains a need for a pocketed spring assembly which incorporates multiple strings of springs without using glue, thereby providing a stronger pocketing spring assembly.
There is also a need for a pocketed spring assembly for use in a bedding or seating product having improved or increased airflow through the pocketed spring assembly to cool the pocketed spring assembly.